1. Field of the Invention
The present invention relates to a structure of an analysis, inspection, or measurement apparatus including a sample analysis apparatus, a shape measurement apparatus, and a probe microscope for measuring shape information such as surface roughness or a step of a sample surface, or physical information such as a dielectric constant or viscoelasticity.
2. Description of the Related Art
In recent years, a probe microscope including an atomic force microscope (AFM) with atomic resolution has been expected for shape measurement to evaluate a fine shape. The atomic force microscope which is a type of probe microscope has been expected as means for observing a surface shape of a novel insulating material and the study thereof has been advanced since G. Binnig, et al., who invented a scanning tunneling microscope (STM), devised the atomic force microscope (see, for example, G. Binnig, C. F. Quate, and Ch. Gerber, “Atomic Force Microscope”, Physical Review Letters, American, Physical Society, 1986, Vol. 56, No. 9, p. 931).
The principle of the probe microscope is as follows. A physical force acting between a sample and a probe whose tip end is sufficiently sharpened is measured as a displacement of a spring element attached with the probe. A surface of the sample is scanned so as to maintain the amount of displacement of the spring element to a constant value. A control signal for maintaining the amount of displacement of the spring element to the constant value is used as shape information to measure the shape of the surface of the sample.
Examples of means for detecting the displacement of the spring element include an optical system and a self detection system for detecting deformation distortion of the spring element as an electrical signal.
Examples of the optical system which have been reported include a system using a so-called interference method (see, for example, R. Erlandsson, G. M. McClelland, C. M. Mate, and S. Chiang, “Atomic force microscopy using optical interferometry”, Journal of Vacuum Science Technology, March/April 1988, A6(2), pp. 266-270) and a system called an optical lever system for emitting laser light to a spring element and detecting a positional deviation of reflected light by a photo detector to generate a displacement signal (see, for example, S. Alexander, L. Hellemans, O. Marti, J. Schneir, V. Elings, P. K. Hansma, Matt Longmire, and John Gurley, “An atomic-resolution atomic force microscope implemented using an optical lever”, Journal of Applied Physics, 1989, 65(1), pp. 164-167). Each of the systems is mainly used as a detection system for the probe microscope.
In recent years, the following self detection system has been known in which a lever portion having a probe provided at the tip end thereof and a support portion supporting the lever portion are connected to each other by two bending portions used as regions for forming two piezoelectric resistors, and a resistance difference between the piezoelectric resistors, indicating a displacement difference between both the bending portions which is caused by the twisting of a cantilever is measured to control the cantilever (see, for example, JP 2006-098794 A, FIG. 1).
A probe microscope in which a probe opposed to a sample receives an interatomic force from the sample is called the atomic force microscope, and a probe microscope in which a probe receives a magnetic force from a sample is called a magnetic force microscope. Therefore, such probe microscopes can detect various forces generated from the samples to observe states of the samples.
FIG. 8 illustrates a structure of a normal probe microscope. A sample 51 to be measured is placed on a fine movement mechanism 52 for three-dimensionally moving the sample. The fine movement mechanism 52 normally includes piezoelectric elements deformed in response to an applied voltage, and finely adjusts a position of the sample relative to a probe 53 opposed to the sample. The probe 53 is provided at a tip end of a cantilever 54 which is a beam member supported at only one end. FIG. 9 illustrates a normal shape of the cantilever. A cantilever substrate 64 is provided with the cantilever 54 which is the beam member supported at only one end. The probe 53 is formed at the tip end of the cantilever 54 and has mainly a triangular or square pyramid shape or a circular cone with a height of 1 μm to 2 μm. The cantilever substrate 64, the cantilever 54, and the probe 53 are made of silicon or a silicon-based material and integrally formed by processing using, for example, an anisotropic etching technique.
The cantilever substrate 64 including the cantilever 54 is held by a cantilever holder 55. The fine movement mechanism 52 is located on a mechanical alignment mechanism (rough movement mechanism) 56, such as a stage, for bringing the sample 51 and the probe 53 close to each other. A displacement detection system 57 for detecting deformation of the cantilever based on a physical amount such as an interatomic force, which the probe receives from the surface of the sample, is provided on the cantilever side. An optical lever system for enlarging distortion deformation of the cantilever by laser light from a laser transmitter 58 and for detecting a positional displacement of the laser light by a photo detector 59 is normally used as the displacement detection system. A signal from the displacement detection system 57 is sent through an amplifier 60 to a Z-axis control feedback circuit 61 for controlling a Z-axis (vertical direction) interval between the sample 51 and the probe 53 to perform scanning with the fine movement mechanism 52, thereby controlling a Z-axis positional relationship between the sample 51 and the probe 53. In-plane scanning between the sample 51 and the probe 53 is performed by scanning with the fine movement mechanism based on a signal from an XY-driver circuit 62. The Z-axis control and the XY-driving are performed by a computer and a control system 63. An in-plane shape of the sample and physical properties thereof are visually imaged based on the control signals.
In the example described above, the sample is three-dimensionally moved during scanning. The fine movement mechanism may be provided on the probe side. A mechanism for performing in-plane (two-dimensional) alignment between the sample and the probe (such as stage) may be provided on the probe side or the sample side.
In particular, when the sample is large, a normal structure is as follows. The fine movement mechanism is provided on the probe side. The sample is opposed to the probe. An in-plane moving means such as a stage mechanism, for moving the sample is provided in order to cover an operation region of the fine movement mechanism.
Examples of the large sample include a silicon wafer and a glass substrate. Several probe microscopes for measuring the large samples have been studied (see, for example, JP 2006-098794 A (FIG. 1), JP 2002-350320 A (FIGS. 1, 7, and 9), JP 2002-350321 A (FIGS. 5 and 6), JP 2005-061877 A (FIGS. 8 and 9), and JP 10-282118 A (FIGS. 1 and 2)).
The probe microscope for measuring the wafer or the glass substrate normally includes the probe and the fine movement mechanism for performing three-dimensional scanning with the probe, which are opposed to an object to be measured, and is described with reference to FIGS. 10 and 11.
A unit section 71 having a detection function is normally provided above a vibration isolation table surface plate 72 for suppressing the transmission of floor vibration, and contained in an acoustic insulating cover for suppressing the transmission of surrounding acoustic vibration. The unit section 71 is located on a base 74 provided on the vibration isolation table surface plate 72 through elastic materials 73. A rough alignment mechanism 76 for aligning a sample 75 in an in-plane direction, an XY-stage in this example, is provided above the base 74. The sample 75 is held above the XY-stage through a sample table 77. A detection means support structure member 78 is provided on the base 74. A Z-axis stage 79 which is a vertical direction alignment mechanism is held to the detection means support structure member 78, and a fine movement mechanism 80 which is a fine alignment mechanism is held thereto through the Z-axis stage 79. A cantilever 81 is held to a tip end of the fine movement mechanism 80. The probe provided at a tip end of the cantilever 81 is aligned to a surface of the sample 75 by the Z-axis stage 79. Distortion deformation of the cantilever 81 relative to the surface of the sample which is caused by the in-plane operation of the fine movement mechanism 80 is detected by an optical lever mechanism (not shown) provided in the fine movement mechanism 80, to control the fine movement mechanism 80 in the vertical direction, thereby measuring the physical properties of the surface of the sample or the shape thereof based on information obtained by the three-dimensional operation of the probe. In this example, an optical microscope 82 for observing the position of the sample is provided. The optical microscope is constructed such that an objective lens can be replaced by an electrically driven revolver. An image is displayed on a monitor or a display through a CCD camera.
As described above, the sample which is the object to be observed is located, through the sample holder, on the in-plane moving mechanism (stage) for shifting the sample observation position. The detection portion is opposed to the sample, and the cantilever is attached to the end of the detection portion. The detection means is held to the detection means support structure member through the moving mechanism for aligning the probe provided at the tip end of the cantilever to an interatomic force detection position which is an observation region. In particular, when the sample which is the object to be observed is large, the support portion structure supporting the detection means has a gate shape, and thus requires at least a structure width larger than an outer size of the sample. The resolution of the apparatus is determined based on the detection capacity of the detection portion and the resistance of the apparatus to disturbance. With respect to the resolution of the atomic force microscope, when the rigidity of, an apparatus structure, particularly, the support structure member of the detection means is low, a relative position between the probe and the surface of the sample opposed to the detection portion varies to induce a reduction in resolution. A disturbance vibration causes an increase in contact frequency between the probe and the surface of the sample, and hence it is likely to break the tip end of the probe, thereby causing a reduction in resolution.